1. Field of the Invention
The present invention relates to an arrangement of a car body structure of a railway car, a monorail car or the like.
2. Description of the Related Art
A railway car body structure is composed of a roof construction constituting the upper face thereof, two side constructions constituting the side walls thereof, an underframe constituting the lower face thereof, and two end constructions constituting the ends thereof. In recent years, in order to mainly reduce the weight of the car body and to improve the productivity thereof, hollow extrusions made of aluminum alloy are used to construct the roof construction, the side constructions and the underframe, and extrusions with ribs made of aluminum alloy are used to construct the end constructions. This art is disclosed in Japanese Patent No. 2604226 (patent document 1).
In a railway car, it is necessary to suppress the bending vibration in the up-down (vertical) direction so as to ensure a good riding quality. In order to suppress the bending vibration, it is effective to improve the flexural rigidity of the car body structure, and actual methods for doing so include “increasing the second moment of area of the car body structure” and “increasing the modulus of longitudinal elasticity of the material used for the car body structure”.
The most effective means for increasing the second moment of area of the car body structure is to expand the height and width of the car body structure. However, this is not practical since it causes interference with the surrounding infrastructure facilities.
Thus, the practical and effective means for increasing the second moment of area of the car body structure is to increase the thickness of the members constituting the car body structure. However, if the thickness of all the members constituting the car body structure is increased, the mass of the whole structure is increased greatly. Moreover, similarly, if the modulus of longitudinal elasticity of all the material used for the car body structure is increased, the mass of the whole structure is also increased greatly. This is because in general, a material having high modulus of longitudinal elasticity also has high density.